Radial gas expander

ABSTRACT

This radial gas expander is provided with a rotating shaft, an impeller which is fixed to the rotating shaft, and a casing by which the rotating shaft is supported in a rotatable manner and in which an introduction channel introducing fluid to the impeller is formed. The introduction channel includes a nozzle blade which guides fluid flowing into the impeller and a support member which is provided in the upstream side of the nozzle blade and which supports wall surfaces of the introduction channel, wherein the wall surfaces are mutually opposed, and the support member has a wing shape in a cross-sectional view.

TECHNICAL FIELD

The present invention relates to a radial gas expander (a radial flowgas expander) in which impellers are arranged on a single shaft inmultiple stages.

Priority is claimed on Japanese Patent Application No. 2011-190525,filed Sep. 1, 2011, the content of which is incorporated herein byreference.

BACKGROUND ART

The gas expander is used to suction and expand high pressure gasdischarged from a plant, convert pressure energy of the gas into speedenergy (mechanical energy), and thus, recover power and reduce the powerof a driving motor or the like.

In recent years, a gas expander which corresponds to higher pressureenergy has been required. As such a gas expander, a radial gas expanderin which a plurality of impellers is provided in multiple stages isknown. As an example of the radial gas expander, a geared(speed-increasing gear) radial gas expander is known, which isconfigured of a driving gear, a speed-increasing gear configured of apinion gear engaging with the driving gear, and a plurality of impellersdisposed in a pinion shaft (for example, refer to Patent Document 1).

Moreover, a radial gas expander is also known in which the plurality ofimpellers are arranged between bearings on a single shaft and theimpellers are built in a single casing. In the radial gas expander inwhich the plurality of impellers are arranged on the single shaft, theshaft is the single shaft in spite of including the multistage impeller.Accordingly, compared to the geared radial gas expander or the like, thenumber of high-pressure seals or high-pressure casing can be reduced toa minimum, and a radial gas expander having high reliability can berealized even in a higher pressure condition (for example, refer toPatent Document 2).

As shown in FIGS. 5 and 6, a radial gas expander 101 of the related artincludes a casing 2, a rotating shaft 3 which is rotatably provided inthe casing 2, and a plurality of impellers 4 which are fixed to therotating shaft 3.

The radial gas expander 101 includes two gas expander sections 105 a and105 b to expand the gas in the inner portion of the gas expander. Thecasing 2 is configured of a casing main body 6 and a diaphragm group 7including a plurality of diaphragms which are built in the casing mainbody 6 and integrally connected. The gas expander sections 105 a and 105b are configured to connect a plurality of diaphragms 8, 9 a, 9 b, 10 a,10 b, 11 a, 11 b, 12 a, 12 b, 13 a, and 13 b, in which return bendsconnecting stages are formed, in an axial direction.

The expander section 105 a and 105 b includes gas introduction channels120 a and 120 b communicating with suction ports 18 a and 18 b of thecasing 2 and gas outflow channels 21 a and 21 b communicating withdischarge ports 19 a and 19 b of the casing 2 in each section.

Among these, the gas introduction channels 120 a and 120 b are definedbetween the center diaphragm 8 which is provided in the center betweentwo gas expander sections 105 a and 105 b and diaphragms 9 a and 9 bwhich are nearest to the center among the plurality of diaphragms exceptfor the center diaphragm 8.

Nozzle blades 24, which generate a gas flow corresponding to profiles ofthe impellers 4, are provided in the upstream side of the impellers 4 onthe gas introduction channel 120.

In the radial gas expander 101 having the above-described configuration,after the gas introduced via the suction port 18 a from a plant (notshown) is expanded in one gas expander section 105 a, the gas isintroduced to the other gas expander section 105 b via gas pipes 22 andthe suction port 18 b and is further expanded.

However, in the radial gas expander 101 of the related art, in order tosecure channel widths of the gas introduction channel 120 a and the gasintroduction channel 120 b, spacers 125 are installed in the upstreamsides of the nozzle blades 24 of the gas introduction channels 120 a and120 b.

RELATED ART DOCUMENTS Patent Document

[Patent Document 1] Japanese Patent No. 3457828

[Patent Document 2] Japanese Unexamined Patent Application, FirstPublication No. 2011-43070

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, since the spacers 125 are installed in the upstream sides ofthe nozzle blades 24, there is a problem that a flow of the gas flowinginto the nozzle blades 24 is disturbed. As shown in FIG. 6, when astreamline L of the introduced gas is disturbed by the spacers 125, lossoccurs when the gas flows into the nozzle blades 24. Moreover, since thespacers are installed in the vicinity of inlets of the gas introductionchannels 120 a and 120 b, reduction effects of an introduction channelwidth change are decreased due to differential pressure. Accordingly, agas flow rate is changed according to the change of the channel width, adesired gas flow rate is not generated when the gas flows into thenozzle blades 24, and loss occurs. In this way, the spacers 125 impedeexpansion performance of the impellers 4, and furthermore, a decrease inthe performance of the radial gas expander 101 occurs.

The present invention is made in consideration of the above-describedcircumstances, and an object thereof is to provide a radial gas expandercapable of obtaining a desired performance. Moreover, an object thereofis to provide a radial gas expander capable of securing the channelwidths of the gas introduction channels 120 a and 120 b and preventingwalls of diaphragms configuring the casing from being deformed.

Means for Solving the Problems

In order to achieve the above-described objects, the present inventionprovides the following means.

According to a first aspect of the present invention, a radial gasexpander includes: a rotating shaft; an impeller which is fixed to therotating shaft; and a casing by which the rotating shaft is supported ina rotatable manner and in which an introduction channel introducingfluid to the impeller is formed. Moreover, the introduction channelincludes: a nozzle blade which guides fluid flowing into the impeller;and a support member which is provided in an upstream side of the nozzleblade and which supports wall surfaces of the introduction channel,wherein the wall surfaces are mutually opposed. In addition, the supportmember has a wing shape in a cross-sectional view.

According to this configuration, distances from lower ends of themutually opposing wall surfaces of the introduction channel provided inthe casing to supporting points are shortened due to the support member,a deformation amount of the opposing wall surfaces can be decreased, anda desired channel width can be secured. Moreover, since the supportmember is formed in the wing shape in a cross-sectional view, the flowof the fluid flowing into the nozzle blade can be prevented from beingdisturbed.

Moreover, according to a second aspect of the present invention, aradial gas expander includes: a rotating shaft; two sets of impellergroups which are configured of impellers fixed to the rotating shaft,and are symmetrically provided in an axial direction;

and a casing by which the rotating shaft is supported in a rotatablemanner, and in which a first introduction channel which introduces fluidto an impeller group of a first set, and a second introduction channelwhich is provided to be adjacent to the first introduction channel andintroduces the fluid discharged from the impeller group of the first setto an impeller group of a second set are formed. Moreover, the secondintroduction channel includes: a nozzle blade which guides fluid flowinginto the impeller; and a support member which is provided in an upstreamside of the nozzle blade and which supports wall surfaces of the secondintroduction channel, wherein the wall surfaces are mutually opposed,and the support member has a wing shape in a cross-sectional view.

According to this configuration, a desired channel width can be securedin the first introduction channel and the second introduction channel.Moreover, even when a pressure difference between the fluid flowing intothe first introduction channel and the fluid flowing into the secondintroduction channel is large, the deformation amounts of a center walland the mutually opposing wall surfaces of the second introductionchannel can be decreased due to the support member, and since thesupport member is formed in the wing shape in a cross-sectional view,the flow of the fluid flowing into the nozzle blade can be preventedfrom being disturbed.

According to a third aspect of the present invention, a plurality of thesupport members are provided around the rotating shaft, and a width ofthe support member is formed to be gradually narrowed from an outercircumferential in a radial direction toward an inner circumferential sothat clearances between the support members are equal in the radialdirection.

According to this configuration, the fluid passing through the vicinityof the support member can be smoothly introduced to the nozzle bladewithout an increase in flow rate of the fluid.

Moreover, according to a fourth aspect of the present invention, thecasing includes a casing main body and a plurality of diaphragms whichare built in the casing main body and are integrally connected. Theintroduction channel is formed in the plurality of diaphragms.

According to this configuration, the casing, to which the nozzle bladeand the support member formed in the wing shape are incorporated, can beeasily assembled. Moreover, maintenance of an inner portion can beeasily performed.

Effect of the Invention

According to the present invention, a radial gas expander, which obtainsdesired performance and can decrease the deformation amount of the wallof the diaphragm configuring the casing, can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a radial gas expander according toan embodiment of the present invention.

FIG. 2 is an enlarged view of a portion A of FIG. 1.

FIG. 3 is a view when viewed from B of FIG. 2.

FIG. 4 is a view showing a streamline of gas which flows around asupport blade.

FIG. 5 is a cross-sectional view of a radial gas expander of the relatedart.

FIG. 6 is a view when viewed from C of FIG. 5, and is a view showing astreamline of gas which flows around a spacer.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described in detail withreference to the drawings.

As shown in FIGS. 1 and 2, a radial gas expander 1 according to theembodiment of the present invention includes a tubular casing 2, arotating shaft 3 which is supported to the casing 2 in a rotatablemanner and extends in an axial direction of the casing 2, and aplurality of impellers 4 which are fixed to the rotating shaft 3.

Moreover, in descriptions below, the axial direction of the casing 2coincides with the axial direction of the rotating shaft 3. Moreover,the axial direction of the casing 2 and the axial direction of therotating shaft 3 are simply referred to as the axial direction.

The radial gas expander 1 includes two sections to expand gas in theinner portion. That is, the radial gas expander 1 includes two gasexpander sections 5 a and 5 b which are configured of a gas expandersection 5 a which is disposed in a first side of the axial direction anda gas expander section 5 b which is disposed in a second side of theaxial direction.

The radial gas expander 1 of the present embodiment has a configurationwhich obtains a rotating drive force by the gas introduced to the firstgas expander section 5 a and further obtains a rotating drive force byintroducing the expanded gas discharged from the first gas expandersection 5 a to the second gas expander section 5 b.

The casing 2 includes a casing main body 6 and a diaphragm group 7 whichis provided in the inner portion of the casing main body 6. Thediaphragm group 7 is configured of eleven diaphragms 8, 9 a, 9 b, 10 a,10 b, 11 a, lib, 12 a, 12 b, 13 a, 13 b which are configured to becapable of being pulled off in the axial direction.

The first gas expander section 5 a includes the diaphragm 8 which isdisposed in the center and the diaphragms 9 a, 10 a, 11 a, 12 a, and 13a which are connected in a first side of the diaphragm 8. Moreover, thesecond gas expander section 5 b includes the diaphragm 8 which isdisposed in the center and the diaphragms 9 b, 10 b, 11 b, 12 b, and 13b which are connected in a second side of the diaphragm 8.

That is, two gas expander sections 5 a and 5 b have the centraldiaphragm 8 as a common component.

A suction port 18 a for introducing the gas to the first gas expandersection 5 a and a suction port 18 b for introducing the gas to thesecond gas expander section 5 b are formed in the casing main body 6.

Moreover, a discharge port 19 a for discharging the gas from the firstgas expander section 5 a and a discharge port 19 b for discharging thegas from the second gas expander section 5 b are formed in the casingmain body 6.

In addition, the discharge port 19 a of the first gas expander section 5a and the suction port 18 b of the second gas expander section 5 b areconnected by a gas pipe 22.

The rotating shaft 3 is disposed to penetrate the center of thediaphragm group 7. Both end portions of the rotating shaft 3 aresupported to diaphragms 13 a and 13 b, which are end plates of each oftwo gas expander sections 5 a and 5 b, in a rotatable manner viabearings 15. Moreover, dry gas seals 16 are provided in the innercircumferences of the diaphragms 13 a and 13 b which are positionedinside each bearing 15.

The plurality of impellers 4 are fixed onto the rotating shaft 3, andimpellers 4 of four stages configuring the first gas expander section 5a and impellers 4 of four stages configuring the second gas expandersection 5 b are arranged so as to be opposite to each other.

In each impeller 4, when the opening portion which opens toward theouter circumferential in the radial direction of the impeller 4 is setto an inlet port 41 and the opening portion which opens toward the axialdirection is set to a discharge port 42, the impellers 4 of four stagesconfiguring the first gas expander section 5 a and the impellers 4 offour stages configuring the second gas expander section 5 b are disposedso that in which the inlet ports 41 are positioned at sides of thecentral diaphragm 8. That is, the impellers 4 configuring the first gasexpander section 5 a are disposed so that the discharge port 42 facesthe first side of the axial direction, and the impellers 4 configuringthe second gas expander section 5 b are disposed so that the dischargeport 42 faces the second side of the axial direction.

Moreover, although the same reference numerals are attached to theplurality of impellers 4, the sizes of the plurality of impellers 4 aredifferent from one another. Specifically, the sizes of the plurality ofimpellers 4 are changed to adapt to an expansion stroke of the gas.

A first introduction channel 20 a and a second introduction channel 20 bwhich communicate with the suction ports 18 a and 18 b respectively areformed between the diaphragms 9 a and 9 b which are positioned in bothsides of the central diaphragm 8. That is, the first introductionchannel 20 a of the first gas expander section 5 a is formed between awall surface 81 of the first side of the central diaphragm 8 and a wallsurface 91 of the second side of the diaphragm 9 a. Moreover, the secondintroduction channel 20 b of the second gas expander section 5 b isformed between a wall surface 82 of the second side of the centraldiaphragm 8 and a wall surface 92 of the first side of the diaphragm 9b.

Accordingly, the first introduction channel 20 a and the secondintroduction channel 20 b are disposed to be adjacent to each other viathe central diaphragm 8.

Similarly, outlet channels 21 a and 21 b, which communicate with theabove-described discharge ports 19 a and 19 b respectively, are formedbetween the diaphragms 13 a and 13 b which are end plates and thediaphragms 12 a and 12 b adjacent to the diaphragms 13 a and 13 b.

Among these, the outlet channel 21 a of the first gas expander section 5a communicates with the discharge port 19 a of the casing main body 6,and the outlet channel 21 b of the second gas expander section 5 bcommunicates with the discharge port 19 b of the casing main body 6.

A plurality of nozzle blades 24, which guide the inflow of the gas tothe impellers 4, are provided in the upstream sides of the impellers 4in each of the first introduction channel 20 a and the secondintroduction channel 20 b. In the present embodiment, 17 nozzle blades24 are provided.

As shown in FIG. 3, the nozzle blades 24 are disposed at equal intervalsin the circumferential direction. Each nozzle blade 24 has a wing shapein which a leading edge is round and a trailing edge is sharp in across-sectional shape when viewed in the axial direction. Moreover, inthe nozzle blades 24, the leading edges are disposed in the outercircumferential side of diaphragm in the circumferential direction, thetrailing edges are disposed in the inner circumferential side ofdiaphragm in the circumferential direction, and the nozzle blades 24 aredisposed to be inclined in a rotating direction in a rotation directionR with respect to the leading edges so that the trailing edges are alongthe rotation direction R of the rotating shaft 3. That is, front endsare disposed in the upstream in the flow direction of the gas, and rearends are disposed in the downstream.

In addition, for example, the cross-sectional shape of the nozzle blade24 is determined using Computational Fluid Dynamic (CFD) analysis.Accordingly, the cross-sectional shape of the nozzle blade 24 of thepresent embodiment is formed to be asymmetrical with respect to a centerline along the flow direction (hereinafter, referred to as a streamlinedirection) of the gas. That is, the nozzle blade 24 has a shape whichsmoothly introduces the flow of the gas to the impeller 4 to promote anoperation which expands and accelerates the gas in the impeller 4.

A plurality (seventeen sheets) of support blades 25 which are supportmembers are provided in the further outer circumferential side of thenozzle blade 24. Similar to the nozzle blades 24, the support blades 25are disposed at equal intervals in the circumferential direction. Eachsupport blade 25 has a so-called wing shape in which a leading edge isround and a trailing edge is sharp in a cross-sectional shape whenviewed in the axial direction. Moreover, in the support blades 25, theleading edges are disposed in the outer circumferential side ofdiaphragm in the circumferential direction, the trailing edges aredisposed in the inner circumferential sides of diaphragm in thecircumferential direction, and the support blades 25 are disposed to beinclined in the rotating direction in the rotation direction R withrespect to the leading edges so that the trailing edges are along therotation direction R. That is, in the support blades 25, the front endsare disposed in the upstream in the streamline direction, and the rearends are disposed in the downstream.

Moreover, the shapes of the support blades 25 are formed so that a widthof the support blade 25 is gradually narrowed from the outercircumferential in the radial direction toward the innercircumferential. Moreover, clearances W between the support blades 25are approximately equal in the streamline direction, that is, the radialdirection.

In addition, the cross-sectional shape of the support blade 25 isdifferent from that of the nozzle blade 24 and is formed to besymmetrical with respect to the center line along the streamlinedirection. The shape, the position in the circumferential direction, andthe position in the radial direction of the support blade 25 are alsodetermined using CFD or the like so as to influence the gas introducedto the nozzle blades 24 as little as possible, and particularly, it ispreferable that the shape of the support blade has a shape along thestreamline. Moreover, it is preferable that the length in the streamlinedirection be set within a range in which the influence to the streamlineis small (which does not disturb the streamline) and be shortened asmuch as possible. In addition, since the streamline is changed accordingto a flow rate of the gas, it is preferable that the flow rate beappropriately determined according to the use conditions.

In the intermediate diaphragms 9 a, 10 a, 11 a, 12 a, 9 b, 10 b, 11 b,and 12 b in each of the gas expander sections 5 a and 5 b, a return bend(intermediate channel) 27 having an U-shaped cross-section is formedwhich connects the discharge port 42 of the impeller 4 in the precedingstage and the inlet port 41 of the impeller 4 in the subsequent stage.Seventeen sheets of return vanes 28 are provided in the return bend 27so that the gas flow to the nozzle blade 24 positioned in the upstreamside of the impeller 4 and the inlet port 41 of the impeller 4 in thesubsequent stage is efficient.

An operation of the radial gas expander 1 having the above-describedconfiguration will be described. First, the gas having high temperatureand high pressure is introduced to the first gas expander section 5 avia the suction port 18 a from a predetermined plant. In the first gasexpander section 5 a, the suction and expansion are repeated over fourstages by the impellers 4 of four stages, and the gas is discharged fromthe discharge port 19 a. Subsequently, the gas is introduced to thesecond gas expander section 5 b via the gas pipe 22 and the suction port18 b, is expanded in the second gas expander section 5 b, and isdischarged from the discharge port 19 b.

The inflow gas flows in the axial direction in the inner portion of twogas expander sections 5 a and 5 b. However, according to theabove-described configuration, the gas flows in the directions oppositeto each other. That is, the gas flows from the second side of the axialdirection to the first side of the axial direction in the gas expandersection 5 a. Moreover, the gas flows from the first side of the axialdirection to the second side of the axial direction in the gas expandersection 5 b.

Here, compared to the pressure of the gas which is introduced to thefirst introduction channel 20 a via the suction port 18 a, the pressureof the gas which is introduced to the second introduction channel 20 bvia the suction port 18 b is low. That is, the pressure differencebetween the pressures in the first introduction channel 20 a and thesecond introduction channel 20 b which are adjacent to each other viathe diaphragm 8 is increased.

According to the above-described embodiment, the pressure differencebetween the pressure in the first introduction channel 20 a and thepressure in the second introduction channel 20 b is increased, and evenwhen a force of a degree as to cause the deformation of the diaphragm 8is applied to the central diaphragm 8 formed between the firstintroduction channel 20 a and the second introduction channel 20 b,deformation amount can be decreased by providing the support blades 25.Moreover, the support blade 25 is formed in the wing shape in across-sectional view, and thus, as shown in FIG. 4, disturbance of thestreamline L of the gas flowing around the support blades 25 can bedecreased.

Moreover, the shapes of the support blades 25 are formed so that a widthof the support blade 25 is gradually narrowed from the outercircumferential in the radial direction toward the innercircumferential. Moreover, clearances W between the support blades 25are equal in the radial direction. As a result, the gas passing throughthe vicinities of the support blades 25 can be smoothly introduced tothe nozzle blade 24 without requiring an increase in flow rate of thegas.

In addition, since the support blade 25 has the shape which issymmetrical in the streamline direction, the support blades can be moreeasily manufactured.

Moreover, since the plurality of diaphragm groups 7 configuring thecasing 2 can be divided in the axial direction, maintenance in the innerportion can be easily performed.

In addition, the technical scope of the present invention is not limitedto the above-described embodiments, and various modifications can beapplied within a scope which does not depart from the gist of thepresent invention. For example, the support blade 25 may have anasymmetrical shape in the streamline direction.

INDUSTRIAL APPLICABILITY

According to the radial gas expander of the present invention, desiredperformance is obtained and the deformation amount of the wall of thediaphragm configuring the casing can be decreased.

DESCRIPTION OF REFERENCE NUMERALS

-   1: radial gas expander-   2: casing-   3: rotating shaft-   4: impeller-   5: gas expander section-   6: casing main body-   7: diaphragm group-   8, 9 a, 9 b, 10 a, 10 b, 11 a, 11 b, 12 a, 12 b, 13 a, and 13 b:    diaphragm-   20 a: first introduction channel (introduction channel)-   20 b: second introduction channel (introduction channel)-   24: nozzle blade-   25: support blade (support member)-   27: return bend

1. A radial gas expander comprising: a rotating shaft; an impeller which is fixed to the rotating shaft; and a casing by which the rotating shaft is supported in a rotatable manner and in which an introduction channel introducing fluid to the impeller is formed, wherein the introduction channel includes: a nozzle blade which guides fluid flowing into the impeller; and a support member which is provided in an upstream side of the nozzle blade and which supports wall surfaces of the introduction channel, wherein the wall surfaces are mutually opposed, and wherein the support member has a wing shape in a cross-sectional view.
 2. A radial gas expander comprising: a rotating shaft; two sets of impeller groups which are configured of impellers fixed to the rotating shaft, and are symmetrically provided in an axial direction; and a casing by which the rotating shaft is supported in a rotatable manner, and in which a first introduction channel which introduces fluid to an impeller group of a first set, and a second introduction channel which is provided to be adjacent to the first introduction channel and introduces the fluid discharged from the impeller group of the first set to an impeller group of a second set are formed, wherein the second introduction channel includes: a nozzle blade which guides fluid flowing into the impeller; and a support member which is provided in an upstream side of the nozzle blade and which supports wall surfaces of the second introduction channel, wherein the wall surfaces are mutually opposed, and wherein the support member has a wing shape in a cross-sectional view.
 3. The radial gas expander according to claim 1, wherein a plurality of the support members are provided around the rotating shaft, and a width of the support member is formed to be gradually narrowed from an outer circumferential in a radial direction toward an inner circumferential so that clearances between the support members are equal in the radial direction.
 4. The radial gas expander according to claim 1, wherein the casing includes a casing main body and a plurality of diaphragms which are built in the casing main body and are integrally connected, and wherein the introduction channel is formed between the diaphragms.
 5. The radial gas expander according to claim 2, wherein a plurality of the support members are provided around the rotating shaft, and a width of the support member is formed to be gradually narrowed from an outer circumferential in a radial direction toward an inner circumferential so that clearances between the support members are equal in the radial direction.
 6. The radial gas expander according to claim 2, wherein the casing includes a casing main body and a plurality of diaphragms which are built in the casing main body and are integrally connected, and wherein the introduction channel is formed between the diaphragms.
 7. The radial gas expander according to claim 3, wherein the casing includes a casing main body and a plurality of diaphragms which are built in the casing main body and are integrally connected, and wherein the introduction channel is formed between the diaphragms.
 8. The radial gas expander according to claim 5, wherein the casing includes a casing main body and a plurality of diaphragms which are built in the casing main body and are integrally connected, and wherein the introduction channel is formed between the diaphragms. 